Field of the Invention
This invention generally concerns industrial water treatment (IWT) systems where often many different conditions arise that require treatment such as corrosion inhibition, scale inhibition, suspended matter dispersion, microbial control, biofilm removal, and biofilm dispersion.
Description of Related Art
Water is used in industry for the transfer of heat in recirculating cooling water systems and production of steam in boilers. There is extensive use of cooling water in most major manufacturing processes to operate efficiently and safely, in commercial air conditioning, and even in domestic air conditioning. Also refineries, steel mills, petrochemical manufacturing plants, electric utilities and paper mills all rely heavily on equipment or processes that require efficient temperature control and often use cooling water to moderate the temperature. Thus these cooling water systems are important to maintain operation of these heat transfer needs in a wide variety of process systems.
Recirculating cooling water systems control temperatures by transferring heat from hot process fluids into cooling water. As this happens, the cooling water itself gets hot and must be cooled by evaporation or secondary chiller system (the water is run through a cooling area or has refrigeration exposure). Water lost in this process must be replaced by a fresh supply of cool water (i.e. makeup water). The makeup water contains dissolved minerals, suspended solids, debris, bacteria, and other impurities. As the water continues to circulate throughout the cooling water system, other contaminants begin to concentrate. The inorganic contaminants, such as scale and corrosion products, may form deposits on heat transfer surfaces and in piping. In addition, biofouling may result by formation of biofilms on surfaces due to growth of microorganisms. These deposits lead to reduction in heat and mass transfer. As a result, the temperature of the system rises, cooling equipment is threatened and a total plant shutdown can result. This can be a very costly outcome.
Clearly, efficient cooling water management is critical to the operation of such plants. Cooling water is a major use of water in industry to transfer heat in such systems. If there is inadequate control, the cooling system can present significant difficulty to the plant in several ways, such as loss of production capacity, increased cost of cleaning, increased cost and use of protective chemicals, increased energy use, increased maintenance costs, and reduction in service life of the system and its components.
Industrial Water Treatment (IWT) uses methods to control multiple issues such as: scale inhibition for example CaCO3 and CaSO4; corrosion inhibition of mild steel, copper, brass and other metals; biofouling inhibition; suspended matter inhibition/dispersion for example rust; cleanup/removal of biofilm and scale deposits; together with issues for safety for exposure to the persons doing this work, and disposal of these agents into the environment. Thus there is a need for a simpler, cost effective way to meet these various issues.
Industrial water treatment methods must control corrosion, scale, biofouling, suspended matter deposition, and microbiological activity. These problems are interrelated and one problem cannot be totally isolated from the others. For example, scaling occurs more rapidly in a corroding system; microbiologically induced corrosion is a potentially serious problem in almost all cooling systems; and under-deposit corrosion can lead to rapid failure of otherwise intact metal.
Another area where similar control of corrosion, scale, biofouling, suspended matter deposition, and microbiological activity is desired occurs in oil production, where water is used in the down-hole oil and gas extraction process.
The science and the practice of water treatment is an on-going and evolving effort. Today, more than ever, with populations increasing, the need for the re-use of water becomes important. Specifically, the use of waste water that has been purified enough for re-use in IWT systems is important to conserve water and is a critical consideration to the entire population and environment. Thus any process that can reduce the use of water is beneficial. A more efficient IWT system, without these problems, can be one way to reduce water usage.
Many attempts have been made to address these various IWT needs. There are many suggestions in the literature; however, they have not worked in a commercial, large scale setting. There are treatments for various aspects of these issues being sold and used. Some of this art is discussed below.
Lamb (U.S. Pat. No. 3,291,683) teaches use of alkoxy or alkylthio-substituted alkyl amines and their acid addition salts as biocides.
Walter (U.S. Pat. No. 4,816,061) teaches use of alkylthioalkylamines and their acid addition salts as biocides to control biofouling in cooling towers.
Nalepa (US Patent Appln. 20090178587) teaches 2-(decylthio)ethanamine as a biocide and biofilm dispersant (biodispersant).
Moir (WO 2005/014491) teaches etheramines and their acid addition salts as biocides for control of sulfate-reducing bacteria to prevent H2S formation and resulting problems including iron sulfide deposits and corrosion present in industrial water systems.
Wolf (U.S. Pat. No. 3,524,719) teaches use of oxyamines and thioamines as steel corrosion inhibitors in sour brines when used in combination with another amine compound such as N,N″-hexachlorobiphenylene)bis(ethylenediamine).
Gartner (U.S. Pat. No. 6,260,561) teaches use of aliphatic amines, including oxyamines, for cleaning swimming pool deposits.
Relenyi (U.S. Pat. Nos. 4,982,004 and 5,025,038) teaches a method of preparation of antimicrobial formulations of thioamine salts but no discussion of their use as scale or corrosion inhibition agents is present. No synergistic effects were described.
Fontana (U.S. Pat. No. 6,183,649) teaches use of thioamine salts as a biofilm remover as part of a multi-component composition to treat water circulating systems for control of white rust (zinc corrosion). No synergistic effects were reported.
2-Hydroxypropane-1,2,3-tricarboxylic acid and other hydroxycarboxylic acids are known in the water treatment industry as chelants, which can dissolve or inhibit inorganic deposits, e.g., calcium and iron salts. This chelant function requires a stoichiometric amount of chelant relative to the inorganic salt [Frayne, C., Cooling Water Treatment: Principles and Practice, pub. Chemical Publishing Company, New York, N.Y., pp 145-146 (1999)]. Furthermore, Amjad (U.S. Pat. No. 4,952,327) teaches that 2-hydroxypropane-1,2,3-tricarboxylic acid is useful to stabilize iron salts in solution and prevent their precipitation; however, it is not a scale inhibitor and is ineffective against carbonate, sulfate, and phosphate salts of calcium. However, it has been reported that 2-hydroxypropane-1,2,3-tricarboxylic acid can act as a “threshold” inhibitor specifically for calcium sulfate scale deposition, which is effective at sub-stoichiometric concentrations (Prisciandaro, M. et al., Ind. Eng. Chem. Res. (2003) 42, 6647-6652). Many carboxylic acids are also known as corrosion inhibitors for ferrous metals, but not for copper and copper-based alloys like brass. Mayer teaches the use of certain carboxylic acids as inhibitors of mild steel corrosion at the indicated web site: (http://www.bkgwater.com/clients/bkgwater/upload/fichiers/sound_corrosion_inhibitors_cooling.pdf).
There are some reports of synergisms between certain amines and carboxylic acids for inhibition of carbon steel and copper corrosion, but synergism for scale inhibition or suspended matter dispersion is not known.
Hollander (U.S. Pat. No. 5,128,065) teaches benefits of using chelant compounds such as 2-hydroxypropane-1,2,3-tricarboxylic acid with triazole-type inhibitors for copper corrosion inhibition in highly corrosive brackish waters. Triazoles are heterocyclic amines but do not have properties typical of most amines, for example, they are much less basic than alkyl amines.
Ochoa (J. Appl. Electrochem. (2004) 34, 487-493) teaches that mixtures of a certain fatty diamine and a phosphonocarboxylic acid produce a synergistic effect for carbon steel corrosion inhibition. There are no salts taught or made and the compounds were only used for carbon steel corrosion.
Kern (Electrochimica Acta (2001) 47, 589-598) teaches an enhanced steel corrosion inhibition by using a basic amine with known carboxylic acid inhibitors, each component contributing to the overall corrosion inhibition. Synergism was not identified or taught.
Amjad (Amjad, Z., presentation AWT-00, Association of Water Technologies, Inc. 12th Annual Convention & Exposition, 2000; also: Tenside Surf. Det. (2007) 44, 88-93) teaches that cationic ammonium species, such as quaternary ammonium salts, have negative effects on performance of poly(prop-2-enoic) acid scale and deposit inhibitors.
Thus many attempts have been made to solve these issues for IWT which requires the use of a variety of different agents to provide the desired control for all the issues needed in the water cooling system. The only known agents used to control two of these issues are: (1-hydroxyethan-1,1-diyl)bis(phosphonic acid) used for both scale and corrosion inhibition, and poly(prop-2-enoic) acids used for scale inhibition and suspended matter dispersion.
Clearly, there is still a need for an IWT compound that can perform multiple functions for all these various needs in an industrial cooling water system, which reduces the number of chemicals needed to accomplish all these above purposes, and allows simpler and more cost effective formulations, while reducing exposure of chemicals to persons, animals and the environment in general.